1. Field of the Invention
In one embodiment, the invention relates to a process for preparing esterified astaxanthin. In a preferred embodiment, the conversion of zeaxanthin esters to esterified astaxanthin is described.
2. Description of the Related Art
Salmonids are attractive due to their characteristic pinkish color of the flesh. In the wild this color comes from the oxygenated carotenoids, mainly astaxanthin, found in organisms that make up their diets. When these fishes are cultivated astaxanthin must be included in their feed. Most of the astaxanthin used by the fish culture industry is produced synthetically by Hoffmann La Roche and BASF. This product is free astaxanthin as a racemic optically inactive mixture of the three isomers (3R, 3′R), (3R, 3′S) and (3S, 3′S).
This carotenoid is very unstable and easily degrades when exposed to air, heat or light needing special protection, handling and storage conditions to avoid oxidation.
Another source of free astaxanthin is produced by fermentation from Phaffia rhodozyma yeast. Esterified astaxanthin is obtained from algal culture of Haematococcus pluvialis. The production of astaxanthin from yeast or algae has not competed successfully with the synthetic product.
The production of free astaxanthin derived from the pigment of marigold flowers is described in U.S. Pat. Nos. 6,372,946 and 6,376,717 both assigned to PRODEMEX and incorporated herein by reference.
In salmonids, the oxycarotenoids are deposited in the flesh in the free form, while in skin, predominantly esters are found. In nature astaxanthin is often present as diester.
Usually the esterified carotenoids are more soluble in lipids than the free carotenoids and this represents an advantage as they can easily be incorporated in the feeds.
Previously Torres-Cardona has discussed the fact that esterified carotenoids like lutein and zeaxanthin show better stability and bioavailability than their free forms when used as pigmenters in poultry and aquaculture and also a process is mentioned for esterification in an aqueous medium. Breivik (WO 00/62625 and WO 03/003848) demonstrated that when free astaxanthin was esterified with short chain omega-3 fatty acids a more stable and efficient carotenoid was obtained for salmonid pigmentation.
Tanaka (JP11290094) reported a process for esterification of astaxanthin with linear or branched carboxylic acids of 14 to 22 carbons using one or several types of lipases for synthesis. Then Anderson describes a general procedure for esterification of astaxanthin using a dehydrating agent which later Gloor (WO 03/066583) adapts to implement a process of industrial interest using the synthetic astaxanthin produced by Hoffmann-LaRoche as a starting material.
An embodiment of the invention describes a method for the production of esterified astaxanthin using zeaxanthin esters as starting material.